There is no health without mental health. As the World Health Organisation states: "Health is a state of complete physical, mental and social wellbeing and not merely the absence of disease or infirmity."

Serious mental illness affects one in six of the UK population at any one time; 16% of adults and 10% of children experience depression and anxiety. Mental illness costs the economy an estimated £110bn a year in treatment costs and lost productivity. But it is also a key risk factor for a host of other causes of sickness and premature death.

This supplement explores the range of interventions that can improve the mental health and wellbeing of the population: from positive parenting programmes and mental first aid training to computer classes for older people.

The New Economics Foundation has summarised the mental health equivalents to the five-a-day physical health message: connect, be active, take notice, keep learning, and give. But there is also the need for government action to lift communities out of poverty, build social cohesion and end the social inequalities.

As a society, we should we doing all we can to avoid and alleviate preventable suffering; as an economy, investment in our mental capital guarantees increased returns.